+1000!
A lot of us take pride in our toughness in riding in all kinds of conditions. But riding when it is icy on the roads, as cyccommute describes, is just plain dumb if the autos are sliding around.
My first winter of commuting was a no prisoners year: freezing fog, snow, rain (of course, Oregon)....the only times I didn't ride was when we were actively having one of our big Pacific storms, I figured that the drivers had too many other things to concentrate on so I didn't add one more variable to the equation.
Now, I think hard about riding in the fog, no freezing fog, snow, and the same rules on the active storms. I can get myself there fine, but don't like to depend on the skills and attentiveness of others any more than I have to. Kinda like driving in the snow - if I'm the only driver out there, I'm fine. But other folk are on the road, too, so I usually stay home.